Roller and roller and breast mills



Nov. 1, 1938. H. E. cox ET AL ROLLER AND ROLLER AND BREAST lEILLS Filed April 27*l 195?.

5 Sheets-Sheet 1 Fig. 1.

Fig. 2,-

/Nl/ENTOR ATTaR/vix Nov.A l, 1938. H. E. cox STAAL '2,135,174

ROLLER ND ROLLER AND BREAST MILLS 3 Sheets-Sheet 2 Filed April 27, 1932 F ig. 3.

Nov. l, 1938. H. E. cox x-:T AL 2,135,174

ROLLER AND ROLLER AND BREAST MILLS Filed April 27, 1932 3 Sheets-Sheet 5 WBV /97'TOR/VE YJ Patented Nov. 1, 1938 UNITED STATES 2,135,174 ROLLER AND ROLLER AND BREAST MILLS Henry Edward Cox, Bristol, and John Rowland Torrance, Bath, England Application April 27, 1932," Serial No.607,830 In., Great Britain June 12, 1931 s claims. (oi.- ca -22) The present invention relates to improvements in or relating to roller and roller and breast mills for grinding and/or reiining paints or iluids or mixtures which become fluid after grinding.

An object of the 'present invention is to realize amore even consistency of the delivered product so that this shall not substantially vary in shade or strength of colour or specific gravity at any stage in progress of the delivery. Thus Where lill the treated material is run' direct from the mill into a succession of like size vessels, the contents of each and every vessel filled from the milllcan be relied upon to be correct to formula or colour shade and weight per unitvolume.

I5. It is well known that when paints, enamels,

inks, etc., are placed in the hopper of a grinding mill in an unground or partially ground condition for final grinding, o1' in a ground` condition for refining there is always a tendency for 20. the oil or other vmedium to be strained off gradually, resulting in a varying consistency of the ground or refined material delivered to the delivery scraper, and often a considerable proportion of the paint, etc., towards the end of the 25 charge passes the rolls in a very dry condition, and not properly ground, as it is diiiicult to grind or break up the colour particles when an insumcient quantity of oil or other mediumis present.

With` paste the'effect is not so serious because 30 the aforesaid separating tendency is not so pronounced in pastes as inliquids and semi-liquids; also as pastes generally have to pass through the mill at least twice, the disadvantage is not so serious as the rolls can beset somewhat coarsely '35 for the first pass so that the separation-effect is to some extent avoided, and this rst pass serves to condition the paste and ensure-better mixing of the colour particles and the medium, so that at the second grinding the tendencyto separate 40 is still further lessened.

When the mill is used for grinding and iinishing liquids and semi-liquid materials thematter becomes more serieuses the separation not only militates against fine grinding, necessitating put# 45 ting the material through the mill several times when once should suilice, but it is also impossible to run the paint, etc., direct from the mill into the tins readyrfor use, as every Vtin varies in proportion of colour to medium and the specific 50 gravity is incorrect, the shade varies and so on, and often there is a percentage of partially dry colour left in the hopper at the end of the run, so that even the bulk would not be correct to for* mula or shade and weight per gallon, etc.

55 With roller mills having a considerable difference in peripheral vspeed of the grinding rolls such as those described in our prior United States Patents 1,713,487 and 1,902,680 this defectbecomes more aggravated, as the higher the difference in periphery speed between the rolls, 5. the greater is vfound to be the tendency towards the aforesaid separation, rand as high peripheral differential is important in obtaining superine grinding-*and finish which is essential for high class peints, enamels, cellulose' products, inks, 1'0` etc., Vthe separation often becomes a serious factor and extremely diilicult to control, sometimes making it necessary to pass the material through the mill :many times at diierent settings of the rolls before the separation can. be sumciently l prevented to give the iinished` product its desiredY qualities.

The present invention, which is applicable to mills with anyy number of rolls and also to mills of the single roller and breast bar type, broadly consistsin so contracting the feeding throat to the .grinding `nip and/or refining slot of the mill that amixing or agitating action, e.'g., a searching Vreturn fiow of material fed to the nip or slot by the roller in excess of the quantity which the roller `and member co-operating therewith to form. the .grinding nip can pass in a giveny time is produced which keeps the colour and medium thoroughly mixed and sets up a throat feed pressure such that the coarser colour is passed gradually through with the finer colour and reduced.

In this `way a iine consistent product is realized which is consistent both as regards Weight and colourthroughout its bulk or separately collected `quantities, and'onlyr the dirt, dross, skins, etc., 35

are rejected owing to their size, and Varying speci'i'lcl gravity.

Thefordinary roller and breast mill has its hopper ybase feed throat face either vertical or substantially so or inclined at an obtuse angle to 40 the roller so thatlittle or no mixing or agitating action or searching return flow of excess material is-produced and the throat feed pressure is so relieved as to be insufiicient to pass the coarser colour which gradually falls back and is deposited on the roll and breast, causing a partial choke which reduces output and promotes the undesirable separation of colour and medium.

In order Vthat the invention lmay be the more readily understood, reference is made to the accompanying drawings which illustrate examples of mills made according to the invention.

In the drawings:- Fig. 1 is. a side elevation, Fig. 2 a plan. Y 55 Fig. 3 a section through the line A-B of Fig.

2, and

, vided in the hopper base |04 so as to allow the hopper contents to drain towards the feed throat 535, and formed or provided on this plate |03 is a downwardly or backwardly projecting portion I0@ which extends into contact with the slow running roll |06 and is so disposed as to form a contracted V throat between the fast running roll |02 and such downwardly projecting portion |00, the narrow end of the throat being towards the grinding nip and/ or refining slot |01.

Such throat surface is thus overhung and leans over or towards the fast running roll |02 and the .resultant action is that the material is thrownl or carried forward to the nip or slot iil'i by the fast running Vroll |02 which is trying to force more material betweenthe rolls |0i, it?, than they can possibly pass. The paint or other material is therefore forced upwards against the throat surface |05 by the oncoming flow of paint being fed to the nip or slot |01 by the fast running roll |02, so that there is a mixing or agitating action or searching return iow of excess material having the mixing and pressure effect hereinabove mentioned.

The hopper base may be a frame casting preferably of bronze, but it can be made of any suitable metal or alloy. The sides |08 of the frame project downwards and are shaped to form the hopper cheeks which are fitted to the contour of the rolls and form the seals at the ends of the rolls, and at the roll contacts.

If desired plates |09 shaped to the contour of the rolls may be provided to form auxiliary adjustable outer sealing plates which may be slotted so that they can be let down or retted as desired.

The portions |I0 of the cheeks forming the seal 1 on the fast running roll are preferably splayed inwards on the roll to prevent the formation of radial grooves on the fast running roll.

Referring to Figs. 5 and 6 it will be seen that the hopper base feed throat of a roller and breast mill is overhung at |20 so as to lean over or towards the roll |2|, being inclined at an acute angle to the horizontal, such acute angle being the angle nearer to the roll |.2|. The breast bar is designated by the referencenumeral |22.

lThe hopper base may be cast in one piece as described and shown fitted into a steel hopper, or the cheeks may be cast separately and the base framed up with suitable end plates, screwed or riveted, or the hopper base can be cast integral withV the hopper in any suitable metal or alloy, and if necessary independent bronze or other metal or alloy sealing plates |23 attached to the hopper base and fitted to the contour of the rolls to form seals. l

It is to be understood that the term grinding -nip in the claims includes refining slot.

We claim:-

l. A roller mill, comprising in combination, fast and slow running rolls, a feed hopper overlying said roll pair, said hopperV having a bottom plate or floor with a discharge opening overlying the fast roll a throat forming plate extending from the edge of said opening nearest the slow roll to the surface of the slow roll adjacent the bight of said rolls, and forming a continuous tapered throat between the fast running roll and said plate, the narrow end of the throat being towards the grinding nip.

2. A roller mill, comprising in combination, fast and slow Vrunning rolls, a feed hopper overlying said roll pair, and having its sides shaped to form end seals for the rolls, said hopper having a bottom plate or floor with aV discharge opening overlying the fast roll, a throat forming plate extending from the edge of said opening nearest the slow roll to the surface of the slow roll adjacent the bight of said rolls, and forming a continuous tapered throat between the fast running roll and said plate, the narrow end of the throat being towards the grinding nip.

3. .A mill for refining paint or similar mate rials containing ne particles of colouring material in a viscous liquid medium comprising in combination, a rotatable roll, a normally stationary grinding bar disposed edgewise to said roll to form a ne, narrow grinding nip, a guide for said bar, said bar being slidable along said guide towards and away from said roll, a hopper overlying the vertical center of the roll adapted to receive the material to be refined and to allow such material to be fed by its own weight on to the periphery of the said roll, a

shallow tapered feed throat which converges towards said nip and terminates at the nip with an approximately radial surface, said feed throat being situated in the lower part of said hopper immediately in advance of the grinding nip and extending substantially unobstructedly over the grinding length of the roll, said feed throat comprising a roof portion in spaced overlying relation with a considerable part of the periphery of said roll, said roof portion being of considerably greater length in the direction of ow than the width of the nip-forming surface of the bar and being inclined upwardly and backwardly with respect to said surface so as to lean over towards the center line of the feed throat to form in conjunction with the periphery of the roll a tapering throat larger at its entrance end than at the nip end, said throat being shaped and proportioned to permit inow and outow of material in the tapering throat in advance of the nip under the propelling action of the roll.

4. A mill for rening paint or similar materials containing particles of colouring matter already brought to a fine state of division and incorporated in a Viscous medium, comprising in combination, a rotatable roll, a member cooperating therewith to form a fine, narrow grinding nip, a hopper overlying the approxi- 'mate vertical center of the roll adapted to receive the material to be refined and allow such material to be fed by its own weight on to the periphery of the said roll, a feed throat in open communication with the hopper which converges towards said nip, said feed throat being defined by a roof portion extending the effective width of the roll and formed separately from said cooperating member and parts movable therewith by a diverging roll-overlying lower wall of said hopper and a floor portion formed by the peripheral surface of said roll, and the narrow end portion of said tapering throat being closed except for the nip by a' transverse wall disposed at a substantial angle relative to the center line of the throat, said roof portion being spaced from and overlying a considerable part of the periphery of said roll so that the width of the throat in the direction of flow is produced at least mainly irrespective of saidfront wall by said roll-overlying wall of the hopper and said roll, the said end wall of the throat and said roof and oor portions being located in advance of the nip and proportioned to deflect excess material carried towards the nip by the roll to flow generally up over the transverse wall and along the roof portion and back towards the hopper and permit the material infront oi' the nip to be kept in a continual state of turbulence whilst the mill is working.

5. A mill for rening paint or similar materials comprising in combination, a rotatable roll, a normally stationary grinding bar disposed edgewise to said roll to form anne, narrow grinding nip, a guide for said bar, said bar being slidable along said guide towards and away from said roll, a hopper overlying the vertical center line of the roll adapted to receive the material to be rened and to allow such material to be fed by its own weight on to the periphery of the said roll, a feed throat in open communication with the hopper Ywhich converges towards said nip, said feed throat being defined by a roof portion formed separately from said grinding bar and the parts movable therewith by a diverging roll-overlying lower wall of said hopper and a floor portion formed by the surface of said roll, the narrow leading portion of said throat being Vclosed except vfor the nip by an approximately radial end wall formed by said bar, means at the side ends of the roll for closing the ends of the said converging throat, said roof portion of the throat being spaced from and overlying a considerable partici the periphery of said roll and being of considerably greater width in the direction of i'lowrof material than the nip-forming surface of saidbarV and being inclined backwardly and upwardly with respect to said surface, the said width of the throat from front to. rear being produced by said roof portion and said roll, said end wall of the throat and said roof and floor portions being proportioned and arranged tddeflect excess material carried into the throat and towards the nip by the roll back towards the hopper and permit the material in Afront of the nip to be kept in a continual state of turbulence whilst the mill is working.

6. A mill for rening paint or similar materials comprising in combination, aV rotatable roll, a second rotatable roll co-operating therewith to form a ne, narrow grinding nip and a hopper overlying the vertical center line of the said rst roll adapted to receive the material tofbe rened and allow suchV material to be fed by its own weight on to the periphery of the said first roll, a feed throat in open communication with the hopper which converges towards said nip, said feed'throat being defined by a roof portion spaced from the said first roll and formed separately from the said rolls by a diverging lower wall of said hopper and a floor portion formed by the surface of said rst roll and a narrow end portion formed by the surface of said second roll, said roof and end portions forming Vtogether a bentpath for the flow of material,

means at the ends of the rolls for closing the ends ofthe throat, said spaced roofv portion overlying a considerable part of the periphery of said first roll so that the width of the throat from beginning to end is produced by said roof portion and said first roll, and the said end wall of the taperingV throat formed by said second roll being of sufficient radial depth to enable excess material carried into the tapering'throat towards the nip by the roll to ow upwardly over the end wall and along the throat adjacent Ythe roo and towards the hopper andpermit the material inA front of the nip to be kept in a` continual state'of turbulence whilst the mill is working. Y

' HENRY EDWARD COX. J. R. TORRANCE. 

